Abstract

This study presents a report on relationship between selected factors and phosphate removal from textile wastewaters using alum. Synthetic textile wastewaters were prepared from poly and ortho-phosphate using standard methods as stated in Standard Methods of Water and Wastewater Analysis. Synthetic and industrial wastewaters were subjected to chemical treatment (coagulation) using alum and combined treatment of biological and chemical treatment. Efficacies of the treatment were based on ability to remove phosphate from the wastewaters. Effects of pH, coagulant dose and initial concentration of phosphate on efficacies of the treatment processes were evaluated statistically. Models that relate alum concentration to phosphate removed were obtained from literature and was solve using least squared, Gaussian elimination and Microsoft excel solver techniques. The equations and methods were evaluated statistically. The study revealed that efficacies of chemical treatment ranges from 0.24 to 0.70, while combined biological and chemical had efficacies ranging from 0.92 to 1.00.Â Removal of phosphate from textile wastewaters by chemical coagulation followed hyperbola pattern with correlation coefficient of 0.9316.Â Parameters for model equation for the treatment processes were k1 = 0.035 and 0.952; k2 = 0.399 and 0.074; k3 = 0.344 and 0.046; and k4 = 0.033 and 0.025 for phosphate from industrial textile wastewater using chemical coagulation and combined biological and chemical coagulation processes respectively. Analysis of the variance of these efficacies revealed that there is significant difference between the treatment process (F = 3.624; p = 0.002) and between the efficacies (F = 37.339; p = 0.000) at 95 % confidence level. It was also revealed that pH, initial phosphate concentration and coagulant dose had effects on efficacies of the treatment processes. Initial phosphate concentration and coagulant dose were significant factors at 95 % confidence level for all the wastewaters and all the methods. It was concluded that initial concentration of the pollutant and pH have effects on effluent quality. Pre-treatment and coagulant dose were significant factors in the treatment of textile wastewaters.